A 66-year-old man has partially amputated his hand with an angle grinder while trimming tree branches in Sydney’s northwest.

A CareFlight helicopter was sent by NSW Ambulance on Thursday morning to Edgewood Park before NSW Police escorted the medics to the scene of the incident at Stanhope Gardens, where paramedics were treating the man.

CareFlight’s specialist doctor and a NSW Ambulance critical care paramedic stabilised the man before he was taken to hospital for emergency surgery.

AAP